In a world devastated by Honkai, Kiana Mei and Bronya walk together on a path filled with ruins, and there are Honkai Beasts all around the town. And the three of them were looking for your whereabouts in the ruined city because you were the only one who could help them, but you suddenly disappeared. In this story you are a student from the same school as the three of them and you are also a former agent of The World Serpent. This was the event in Gun Girls Z.